Avalanche Forecast for Monday, March 23, 2020
This information was published 03/23/2020 at 6:55 AM.
The Bottom Line
Today starts with a hard, icy snowpack that led to several long, sliding falls over the weekend. If you’re heading into steep terrain this morning, carry the appropriate equipment and put it on before it’s too late. Crampons and an ice axe are the bare minimum to help stay safe on this sort of snow. As the evening approaches, snowfall will begin with a significant amount falling overnight. Forecast amounts and timing have a degree of uncertainty, but we believe new snow will begin late enough to not elevate today’s avalanche danger. Avalanche danger today is LOW and the primary hazard for the day is long, sliding falls. When snow begins in the late afternoon, be on the lookout for developing small wind slabs.
The AMC has closed all facilities at Pinkham Notch, including the restrooms. Please plan accordingly until alternatives are in place. The winter pit toilets at Hermit Lake remain open though the store and breezeway at HoJo’s (the caretakers cabin) remain closed along with all shelters and camping.
Yesterday was calm, clear, and chilly. Temperatures on the summit never made it above the single digits and lower elevation snowplots all remained below freezing. Despite the abundant sunshine and calm wind, the snow surface softened enough to tempt skiers, but not enough to provide corn skiing.
Today, clouds will develop and thicken as a low pressure system approaches the area from our south. Wind will be from the S shifting SW at 30-45mph. The bulk of snow will come tonight after dark, but there is a chance we could see a few inches fall before nighttime.
Tomorrow will start with a blanket of snow from Monday night’s storm. Snowfall totals are uncertain, with 4-11” forecast on the summit by the time all is said and done. It looks as if the bulk of precipitation will track to the south of the Presidentials, giving our avalanche forecast area snow, but probably not the higher end of forecast amounts. Tuesday wind will be from the N and NW in the 35-50mph range.
Primary Avalanche Problem – Wind Slab
Wind slabs will develop this evening once it starts snowing. If you are out late this afternoon or evening, this avalanche problem will be forming. As the bulk of snowfall is arriving tonight, we believe that wind slabs that may develop today would be small due to light wind and low accumulation. If you find yourself out late and caught in the snowstorm, recognize the avalanche problem is developing and take the appropriate steps to mitigate the hazard.
What is a Windslab Avalanche?
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Over the weekend, multiple people took long, sliding falls. Thanks to our snowpack being at its max right now with well-developed runouts, these falls resulted in no known injuries. There are great lessons to be learned from these incidents (carry crampons and an ice axe, ski within your ability or well-under your ability given the current situation, down-climbing is always an option), but also recognize that soon our snowpack will start to melt and spring hazards will emerge. If any of this weekend’s falls were to occur later in the spring, it’s possible these folks would have found rocks to hit, crevasses to fall into, or bushes that would grab and start their tomahawk. When backcountry skiing (and for the rest of this season, it’s all backcountry skiing), remember that you are skiing the snowpack underfoot, not the calendar. Just because it’s late March and you always make your pilgrimage to Tuckerman on this date, you still have to assess the snowpack and make safe travel decisions. Maybe this year, the safe travel decision is to stay home.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch.
The Lion Head Winter Route remains the easiest route to the summit from Pinkham Notch but requires an ice axe, crampons (not just micro-spikes) and possibly a rope. This is a mountaineering route and requires solid skills for a safe, timely ascent.
Details on daily snowfall totals, precipitation type, total depth of snow and other information can be found on our page devoted to snow study plot data. Click here to check it out.
Recent snowpack and avalanche observations can be found here and on Instagram. Your observations help improve our forecast product. Please take a moment and submit a photo or two and a brief description of snow and avalanche information that you gather in the field.
Safe travel in avalanche terrain requires training and experience. This forecast is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
Avalanche danger may change when actual weather differs from the higher summits forecast.
For more information contact the US Forest Service Snow Rangers, AMC visitor services staff at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or seasonally at the Harvard Cabin (generally December 1 through March 31). The Mount Washington Ski Patrol is also available on spring weekends.
Posted 03/23/2020 at 6:55 AM.
USDA Forest Service
White Mountain National Forest